Method for efficiently performing initial access in a multi-carrier broadband wireless access system

ABSTRACT

A method for efficiently performing an initial access in an MS in a multi-carrier broadband wireless access system is disclosed. The method includes scanning a plurality of carriers supported by a BS, and selecting one of the scanned carriers as a first carrier and receiving an SFH of the first carrier. The SFH of the first carrier includes at least one of a field indicating load status of the first carrier and recommended network entry carrier information including information about a second carrier in good load status.

This application claims the benefit of U.S. Provisional Application Ser.Nos. 61/122,743, filed on Dec. 16, 2008, which is hereby incorporated byreference as if fully set forth.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system, andmore particularly, to a method for efficiently performing initial accessin a multi-carrier broadband wireless access system.

2. Discussion of the Related Art

An Advanced Mobile Station (AMS) and an Advanced Base Station (ABS)communicate with each other on a plurality of carriers in compliancewith the Institute of Electrical and Electronics Engineers (IEEE)802.16m standard, more efficiently than in a single-carrier environment.For example, from the viewpoint of the AMS, it can use a widerbandwidth, whereas from the viewpoint of the ABS, it can accommodatemore users. Besides IEEE 802.16m, other radio technologies (e.g. LongTerm Evolution-Advanced (LTE-A) support the multi-carrier communication.

A conventional multi-carrier wireless communication system will bedescribed below.

FIG. 1 illustrates examples of using multiple carriers in a conventionalwireless communication system.

Generally, contiguous multiple carriers may be aggregated as illustratedin FIG. 1( a) or non-contiguous multiple carriers may be aggregated asillustrated in FIG. 1( b). A carrier aggregation unit is a basicbandwidth unit in a legacy system (e.g. LTE is a legacy system for LTE-Aand IEEE 802.16e is a legacy system for IEEE 802.16m). In amulti-carrier environment, two types of carriers are typically defined,primary carrier and secondary carrier.

The primary carrier is the carrier used by the ABS and the AMS toexchange traffic and full PHYsical (PHY)/Medium Access Control (MAC)control information. Further, the primary carrier may be used for ageneral AMS operation such as network entry. Each AMS has a singlecarrier that it considers to be its primary carrier for initial networkentry to a cell.

The secondary carrier is an additional carrier that can be used forexchanging traffic according to the ABS's specific allocation commandsand rules, typically received on the primary carrier.

Based on the usage of the primary and/or secondary carrier, the carriersof the multi-carrier system may be classified differently as follows,from the perspective of the ABS.

Fully configured carrier: A carrier for which all control channelsincluding synchronization, broadcast, multicast and unicast controlchannels are configured. Information and parameters regarding amulti-carrier operation and the other carriers may also be included inthe control channels.

Partially configured carrier: A carrier with only an essential controlchannel configuration to support traffic exchanges in the multi-carrierenvironment, that is, a carrier on which only downlink data istransmitted and received.

Preferably, the primary carrier is fully configured, whereas thesecondary carrier is fully or partially configured depending on channelstatus and user requirements. When one of fully configured carriersavailable to a cell is allocated as a primary carrier to an AMS in thecell, the AMS may be controlled through the primary carrier. Inaddition, the AMS may dynamically use a plurality of secondary carriers.In general, the AMS receives information about a secondary carrier aswell as typical control information on the primary carrier, andtransmits and receives data on the secondary carrier or primary carrier.A fully configured carrier allocated as a secondary carrier to an AMSmay be a primary carrier for another AMS.

The IEEE 802.16m standard regulates that an AMS enters an ABS inaccordance with a conventional IEEE 802.16e procedure. Specifically, theAMS synchronizes to the ABS by contention-based Code Division MultipleAccess (CDMA) code ranging, and then performs a network entry procedureby exchanging an Advanced Air Interface Ranging Request (RNG-REQ)message and a Ranging Response (AAI RNG-RSP) message with the ABS.Subsequently, the AMS and the ABS may perform a capability negotiationprocedure.

FIG. 2 is a flowchart illustrating an initial access method in theconventional wireless communication system and FIG. 3 is a diagramillustrating a signal flow for a ranging procedure between an AMS and anABS in the conventional wireless communication system.

Referring to FIG. 2, upon power-on, the AMS searches for an ABS to serveby scanning DownLink (DL) channels. Without initial knowledge of thegeography and configuration of a network, the AMS scans the frequenciesof neighbor ABSs one by one.

After completing every system setting by acquiring Downlink (DL) andUpLink (UL) system information about the detected ABS, the AMS performsa ranging procedure with the ABS, as illustrated in FIG. 3. The AMSacquires UL synchronization by contention-based ranging with the ABSusing a CDMA ranging code.

Until the synchronization is completed, the ABS notifies the AMS ofparameters to be adjusted by an RNG-RSP message. The status of theRNG-RSP message is set to “continue” during the parameter adjustment,and when the parameter adjustment is completed, the ABS transmits anRNG-RSP message with a status set to “success” to the AMS. When the AMSis fully synchronized to the ABS, it registers to a broadband networkand receives services over the broadband network.

If an initial access is performed in the above conventional method in amulti-carrier environment, the AMS should select one of a plurality ofcarriers supported by the ABS, for the initial access. However, theAMS's access to a specific carrier may be rejected depending on the loadstatuses of the carriers of the ABS. Then the ABS attempts an access toanother carrier, thus causing an unnecessary delay. Accordingly, thereexists a need for a method for efficiently performing an initial accessin the AMS, taking into account the load statuses of a plurality ofcarriers supported by the ABS under the multi-carrier environment.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method forperforming an initial access in a multi-carrier broadband wirelessaccess system that substantially obviates one or more problems due tolimitations and disadvantages of the related art.

An object of the present invention is to provide a method forefficiently performing an initial access in a Mobile Station (MS) in amulti-carrier environment.

Another object of the present invention is to provide a method fortransmitting information about the load statuses of multiple carrierssupported by a Base Station (BS) to an MS.

It will be appreciated by persons skilled in the art that that theobjects that could be achieved with the present invention are notlimited to what has been particularly described hereinabove and theabove and other objects that the present invention could achieve will bemore clearly understood from the following detailed description taken inconjunction with the accompanying drawings.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod for efficiently performing an initial access in an MS in amulti-carrier broadband wireless access system includes scanning aplurality of carriers supported by a BS, and selecting one of thescanned carriers as a first carrier and receiving a Super Frame Header(SFH) of the first carrier.

The SFH of the first carrier may include at least one of a fieldindicating load status of the first carrier and recommended networkentry carrier information including information about a second carrierin good load status.

The method may further include determining whether the first carrier isa fully configured carrier, and determining the load status of the firstcarrier based on the field, if the first carrier is a fully configuredcarrier.

If the field indicates that the first carrier is in good load status,the method may further include performing the initial access on thefirst carrier.

If the field indicates that the first carrier is in bad load status, themethod may further include scanning the second carrier about which theinformation is included in the recommended network entry carrierinformation, receiving an SFH of the second carrier, and performing theinitial access on the second carrier.

The initial access may be performed on the second carrier, only if afield indicating load status of the second carrier in the SFH of thesecond carrier indicates that the second carrier is in good load status.

The field may be a cell bar bit field.

The recommended network entry carrier information may includeinformation about at least one of an index, center frequency offset, andbandwidth of the second carrier and may be included as a secondary SFHsubpacket information element in the SFH.

The recommended network entry carrier information may be updated atevery predetermined interval.

In another aspect of the present invention, an MS in a multi-carrierbroadband wireless access system includes a processor, and a RadioFrequency (RF) module for transmitting and receiving RF signals undercontrol of the processor.

The processor may select one of a plurality of carriers supported by aBS, receive an SFH of the selected carrier, the SFH of the selectedcarrier including at least one of a field indicating load status of theselected carrier and recommended network entry carrier informationindicating a recommended carrier in good load status among the pluralityof carriers, and select a carrier on which an initial access is to beperformed using the field and the recommended network entry carrierinformation.

The processor may determine whether the selected carrier is a fullyconfigured carrier and determine the load status of the selected carrierbased on the field, if the selected carrier is a fully configuredcarrier.

If the field indicates that the selected carrier is in good load status,the processor may perform the initial access on the first carrier.

If the field indicates that the selected carrier is in bad load status,the processor may perform the initial access on the recommended carrier.

If the field indicates that the selected carrier is in bad load status,the processor may scan the recommended carrier by controlling the RFmodule and perform the initial access on the recommended carrier.

The processor may control the RF module to receive an SFH of therecommended carrier and perform the initial access on the recommendedcarrier, only if a field indicating load status of the recommendedcarrier in the SFH of the recommended carrier indicates that therecommended carrier is in good load status.

The field may be a cell bar bit field.

The recommended network entry carrier information may includeinformation about at least one of an index, center frequency offset, andbandwidth of the recommended carrier and may be included as a secondarySFH subpacket information element in the SFH.

Accordingly, the present invention provides the following effects and/oradvantages.

First of all, an AMS (or MS) can efficiently perform an initial accessin a multi-carrier environment.

Secondly, the AMS can acquire information about the load statuses ofcarriers supported by an ABS (or BS).

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates examples of using multiple carriers in a conventionalwireless communication system;

FIG. 2 is a flowchart illustrating an initial access method in theconventional wireless communication system;

FIG. 3 is a diagram illustrating a signal flow for a ranging procedurebetween an Advanced Mobile Station (AMS) and an Advanced Base Station(ABS) in the conventional wireless communication system;

FIG. 4 is a flowchart illustrating an exemplary initial access procedureof an AMS according to an embodiment of the present invention;

FIG. 5 is a flowchart illustrating another exemplary initial accessprocedure of an AMS according to the exemplary embodiment of the presentinvention;

FIG. 6 illustrates a specific application example of an initial accessprocedure of an AMS according to the embodiment of the presentinvention; and

FIG. 7 is a block diagram of a transmitting side and a receiving sideaccording to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a wireless communication system.Embodiments of the present invention provide a method for efficientlyperforming an initial access to a Base Station (BS) in a Mobile Station(MS) in a multi-carrier broadband wireless access system.

Embodiments described hereinbelow are combinations of elements andfeatures of the present invention. The elements or features may beconsidered selective unless otherwise mentioned. Each element or featuremay be practiced without being combined with other elements or features.Further, an embodiment of the present invention may be constructed bycombining parts of the elements and/or features. Operation ordersdescribed in embodiments of the present invention may be rearranged.Some constructions of any one embodiment may be included in anotherembodiment and may be replaced with corresponding constructions ofanother embodiment.

In the description of drawings, procedures or steps, which may ruin thesubstance of the present invention, are not explained. And, proceduresor steps, which can be understood by those skilled in the art, are notexplained as well.

Embodiments of the present invention are supported by standard documentsdisclosed for at least one of wireless access systems including anInstitute of Electrical and Electronics Engineers (IEEE) 802 system, a3^(rd) Generation Project Partnership (3GPP) system, a 3GPP Long TermEvolution (LTE) system, and a 3GPP2 system. In particular, the steps orparts, which are not described to clearly reveal the technical idea ofthe present invention, in the embodiments of the present invention maybe supported by the above documents. All terminologies used herein maybe supported by at least one of IEEE 802.16 standard documents,P802.16-2004, P802.16e-2005, and P802.16Rev2 (P802.16-2009).

Now a detailed description will be made of preferred embodiments of thepresent invention with reference to the accompanying drawings. Thefollowing detailed description presented with reference to theaccompanying drawings is intended to describe not the only embodiment ofthe present invention but exemplary embodiments of the presentinvention.

Specific terms used for the embodiments of the present invention areprovided to help the understanding of the present invention. Thesespecific terms may be replaced with other terms within the scope andspirit of the present invention.

It may occur that an Advanced Mobile Station (AMS) fails in networkentry to an Advanced Base Station (ABS). For example, the network entryfailure may result when the ABS is in bad load status or has a poorchannel quality and thus transmits a rejection to the AMS.

In an IEEE 802.16e system, the ABS transmits the rejection to the AMSusually by a Ranging Response (RNG-RSP) message. As the AMS does notknow the rejection until receiving the RNG-RSP message, a rangingprocedure that the AMS has performed using a Code Division MultipleAccess (CDMA) code is unnecessary, thus causing overhead.

To avert the unnecessary overhead, the AMS determines whether to enteran ABS, using a cell bar bit in the IEEE 802.16m system according to thepresent invention. Specifically, the AMS may determine whether the ABSwill reject the network entry of the AMS due to its load status and thusdetermine whether to attempt an initial ranging using a CDMA code, basedon the cell bar bit determination.

The cell bar is 1 bit, which may be broadcast periodically in aSuperFrame Header (SFH) transmitted by the ABS. If the cell bar bit isset to ‘0’, this means that the ABS is in good load status and thus mayaccept an additional network entry of an ABS. If the cell bar bit is setto ‘1’, this means that the ABS is in bad load status and thus may notaccept an additional network entry of an ABS. In case of an ABSsupporting a plurality of carriers, cell bar bits may be set for fullyconfigured carriers respectively among the plurality of carriers.

When a specific ABS to which an AMS attempts a network entry supports aplurality of carriers, the AMS selects one of the carriers and performsthe network entry to the ABS on the selected carrier. For example, it isassumed that the ABS supports four carriers, cell bar bits are set to isfor three of the carriers, and network entry for the AMS is allowed onthe other carrier (i.e. a cell bar bit is set to 0 for the othercarrier). When the AMS intends an initial access to the ABS on a carrierfor which a cell bar bit is set to 1, the network entry may beimpossible in view of the load status of the carrier in the ABS. Thusthe AMS should select another carrier to thereby attempt a networkentry. In other words, the AMS should attempt the network entry until itdetects a carrier for which a cell bar bit is set to 0 from among theplurality of carriers supported by the ABS.

In the worst case, the AMS attempts the network entry sequentially onthe three carriers for which cell bar bits are set to is and the networkentry attempts are rejected. Then the AMS succeeds in the network entryon the last carrier for which a cell bar bit is set to 0.

The unnecessary network entry attempts delay the network entry of theAMS, thereby adversely affecting the Quality of Service (QoS) of aservice sensitive to an interruption time or delay.

To prevent an unnecessary delay that may be involved in an initialnetwork entry of the AMS in the multi-carrier environment, informationabout carriers on which the AMS is allowed to perform an initial accessto the ABS is transmitted to the AMS on at least one of the plurality ofcarriers supported by the ABS in accordance with an embodiment of thepresent invention.

To this end, recommended network entry carrier information istransmitted to the AMS in an SFH of each carrier supported by the ABS.

The recommended network entry carrier information includes informationabout at least one of recommended carriers that are good in load statusand channel quality among the carriers supported by the ABS.

The recommended network entry carrier information may be included onlyin SFHs of fully configured carriers or SFHs of all carriers. Because atleast one recommended carrier indicated by the recommended network entrycarrier information is used for an initial access of the AMS, the atleast one recommended carrier is preferably a fully configured one, forwhich a cell bar bit is set to 0.

The recommended network entry carrier information may include thefollowing information.

-   -   Index of recommended carrier    -   Center frequency offset of recommended carrier    -   Bandwidth of recommended carrier

The statuses of the carriers may vary over time. Hence, the recommendednetwork entry carrier information is preferably updated periodically.That is, it is preferable that information about a best carrier at acurrent time point is broadcast as recommended network entry carrierinformation in an SFH.

The recommended network entry carrier information may be included in oneof SubPackets (SPs) of a Secondary SFH (S-SFH) as illustrated in Table 1below.

Table 1 illustrates an example of an S-SFH SP Information Element (IE)according to an embodiment of the present invention.

TABLE 1 Size Syntax (bit) Notes S-SFH SPx IE format ( ) { May beincluded in any one of the SP IE's (e.g. SP1, SP2, SP3) . . . Recommendnetwork entry Physical carrier index of carrier index recommendedcarrier Carrier frequency offset Frequency offset of recommended carrierfrom the current accessing carrier Carrier Bandwidth Bandwidth ofrecommended carrier . . . }

Referring to Table 1, information about the index, center frequencyoffset, and bandwidth of a recommended carrier may be included in theS-SFH SP. The S-SFH SP may be any of first, second and third S-SFH SPs,S-SFH SP1, S-SFH SP2, and S-SFH SP3.

The above described recommended network entry carrier information maynot included in the SFH of a carrier if the carrier is afully-configured carrier and is good in load status (i.e., the cell barbit is set to ‘0’).

With reference to FIG. 4, an initial access method of an AMS in amulti-carrier environment according to an embodiment of the presentinvention will be described.

FIG. 4 is a flowchart illustrating an exemplary initial access procedureof an AMS according to an embodiment of the present invention.

It is assumed in FIG. 4 that an ABS supports a plurality of carriers,some of which are fully configured and the other carriers of which arepartially configured, and recommended network entry carrier informationis included in SFHs of both the fully configured carriers and thepartially configured carriers.

Referring to FIG. 4, the AMS scans the plurality of carriers supportedby the ABS in step S401 and receives an SFH of a specific carrier amongthe scanned carriers in step S402.

The SFH of the specific carrier may include at least one of a cell barbit and recommended network entry carrier information.

The AMS may determine from the SFH whether the specific carrier is afully configured carrier in step S403.

For example, the determination may be made using a field of the SFH,indicating whether the specific carrier is fully configured, or based onthe presence or absence of UL control information in the SFH.

If the specific carrier is a fully configured one, the AMS checks a cellbar bit in the SFH in step S404.

If the cell bar bit is set to ‘0’, which means that the specific carrieris in good load status, the AMS may attempt an initial access on thespecific carrier in the afore-described initial access method in stepS405.

On the contrary, if the cell bar bit is set to ‘1’ in step S404 or ifthe specific carrier is not fully configured in step S403, the AMSchecks recommended network entry carrier information to acquireinformation about a fully configured carrier in good load status.

As described before with reference to Table 1, the recommended networkentry carrier information includes information about the index, centerfrequency offset and bandwidth of a recommended carrier. Thus, the AMSmay scan for the recommended carrier indicated by the recommendednetwork entry carrier information and receive an SFH of the recommendedcarrier in step S406.

In step S407, the AMS may check a cell bar bit for the recommendedcarrier in the received SFH because the load status of the recommendedcarrier indicated by last updated recommended network entry carrierinformation may be changed at the time when the AMS attempts to accessthe recommended carrier, according to the update period of therecommended network entry carrier information.

If the cell bar bit is set to ‘0’ for the recommended carrier, whichimplies that the recommended carrier is in good load status, the AMS mayattempt the initial access on the recommended carrier in step S408.

On the contrary, if the cell bar bit is set to ‘1’ for the recommendedcarrier, the AMS repeats step S406 for a recommended carrier ranked asecond best if the recommended network entry carrier informationincludes information the second-best recommended carrier. Otherwise, theAMS may attempt the initial access sequentially on the other carrierssupported by the ABS in the general manner in step S409.

FIG. 5 is a flowchart illustrating another exemplary initial accessprocedure of an AMS according to the embodiment of the presentinvention.

It is assumed in FIG. 5 that the AMS receives an SFH of a carrierscanned for an initial access and then does not check a cell bar bit forthe carrier.

Referring to FIG. 5, the AMS scans a plurality of carriers supported byan ABS in order to access the ABS in step S501. In step S502, the AMSreceives an SFH of a specific carrier among the scanned carriers andchecks recommended network entry carrier information in the SFH.

The AMS determines whether the specific carrier is a recommended carrierindicated by the recommended network entry carrier information in stepS503.

If the specific carrier is the recommended carrier, which implies thatthe specific carrier is a fully configured carrier in good load status,the AMS may attempt an initial access on the specific carrier in stepS504.

On the other hand, if the specific carrier is not the recommendedcarrier, the AMS may attempt an initial access on the recommendedcarrier based on information included in the recommended network entrycarrier information in step S505.

A specific application example of the initial access method will bedescribed below with reference to FIG. 6.

FIG. 6 illustrates a specific application example of an initial accessprocedure of an AMS according to the embodiment of the presentinvention.

It is assumed in FIG. 6 that an ABS supports three carriers, f1, f2 andf3, the first carrier f1 is partially configured, and the second andthird carriers f2 and 3 are fully configured. Also, it is assumed thatrecommended network entry carrier information is included in SFHs of allof the fully and partially configured carriers and the third carrier f3is in the best load status.

Referring to FIG. 6, the AMS scans the downlink of the first carrier f1to attempt an initial access to the ABS in step S601 and receives an SFHof the first carrier f1 in step S602.

As assumed, recommended network entry carrier information included inthe SFH indicates the third carrier f3 as a recommended carrier.

In general, since the first carrier f1 is not fully configured and thusthe initial access is impossible on the first carrier f1, the AMSattempts an initial access on the second carrier f2 according to theorder of carrier indexes. However, the AMS scans the third carrier f3indicated by the recommended network entry carrier information in stepS603 and receives an SFH of the third carrier f3 in step S604 in thepresent invention.

The AMS may check a cell bar bit for the third carrier f3. If the cellbar bit is set to ‘0’, the AMS may attempt an initial access to the ABSon the third carrier f3 in step S605.

An AMS and an ABS (femto BS or macro BS) for implementing theabove-described embodiments of the present invention will be describedbelow.

The AMS may serve as a transmitter on a UL and as a receiver on a DL,whereas the ABS may serve as a receiver on the UL and as a transmitteron the DL. Thus the AMS and the ABS each may include a transmitter and areceiver for data transmission and reception.

The transmitter and the receiver each may include a processor, a module,a part and/or means to implement the afore-described embodiments of thepresent invention. Especially the transmitter and the receiver each mayinclude a module (or means) for encrypting a message, a module forinterpreting an encrypted message, and an antenna for transmitting andreceiving messages. An example of the transmitter and the receiver willbe described with reference to FIG. 7.

FIG. 7 is a block diagram of a transmitting side and a receiving sideaccording to another embodiment of the present invention.

Referring to FIG. 7, the transmitting side and the receiving side areshown on the left and right sides, respectively. The transmitting sideand the receiving side may include antennas 5 and 10, processors 20 and30, Transmission (Tx) modules 40 and 50, Reception (Rx) modules and 70,and memories 80 and 90, respectively. The components of the transmittingside are counterparts of the components of the receiving side.

The antennas 5 and 10 transmit signals generated from the Tx modules 40and 50 over the air, or output external radio signals to the Rx modules60 and 70. When Multiple Input Multiple Output (MIMO) is supported, twoor more antennas may be used.

An antenna, a Tx module, and an Rx module may collectively form a RadioFrequency (RF) module.

The processors 20 and 30 provide overall control to the transmittingside and the receiving side. For example, the processors 20 and 30 mayperform a control function according to the embodiments of the presentinvention, a variable MAC frame control function based on servicecharacteristics and a propagation environment, a handover function, andan authentication and encryption function.

Especially the processor of the AMS provides overall control to the AMSby scanning a plurality of carriers supported by the ABS and receivingan SFH of one of the carriers by controlling the RF module.

For example, the processor of the AMS may receive the SFH of the carrierin synchronization to the carrier by controlling the RF module, decodethe SFH, checks a cell bar bit of the carrier in the decoded SFH, andthus identify the load status of the carrier.

In another example, the processor of the AMS may acquire recommendednetwork entry carrier information in a received SFH and acquireinformation about a recommended carrier in good load status among aplurality of carriers supported by the ABS. The information about thecarrier in good load status may include the index, center frequencyoffset, and bandwidth of the carrier.

The recommended network entry carrier information may be included in anS-SFH SP which may be one of S-SFH SP1, S-SFH SP2 and S-SFH SP3.

The processor of the ABS may set cell bar bits for a plurality ofsupported carriers and recommended network entry carrier informationaccording to the load statuses of the carriers, and include the cell barbits and the recommended network entry carrier information in SFHs ofthe carriers.

The Tx modules 40 and 50 may encode and modulate transmission datascheduled by the processors 20 and 30 in a predetermined modulation andcoding scheme and provide the modulated data to the antennas 5 and 10.

The Rx modules 60 and 70 may recover the original data by decoding andmodulating RF signals received through the antennas 5 and 10 and thusmay provide the original data to the processors 20 and 30.

The memories 80 and 90 may store programs for processing and controloperations of the processors 20 and 30 and temporarily storeinput/output data (sleep mode information according to referencesynchronization information). Also, the memories 80 and 90 may includeat least one of a flash memory-type storage medium, a hard disc-typestorage medium, a multimedia card micro-type storage medium, a card-typememory (e.g. an Secure Digital (SD) or extreme Digital (XS) memory), aRandom Access Memory (RAM), a Read-Only Memory (ROM), an ElectricallyErasable Programmable Read-Only Memory, a Programmable Read-Only Memory,a magnetic memory, a magnetic disc, and optical disk.

The ABS may perform, in at least one of the above-described modules orin a separately procured means, module or part, a control functionaccording to the embodiments of the present invention, an OrthogonalFrequency Division Multiple Access (OFDMA) packet scheduling, TimeDivision Duplex (TDD) packet scheduling, channel duplexing, a variableMAC frame control function based on service characteristics and apropagation environment, a real-time high-speed traffic controlfunction, a handover function, an authentication and encryptionfunction, a packet modulation and demodulation function for datatransmission and reception, a high-speed packet channel coding function,and a real-time modem control function.

As is apparent from the above description, an AMS (or MS) canefficiently perform an initial access in a multi-carrier environment.Also, the AMS can acquire information about the load statuses ofcarriers supported by an ABS (or BS).

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein. It is obvious to those skilled in the art thatclaims that are not explicitly cited in each other in the appendedclaims may be presented in combination as an exemplary embodiment of thepresent invention or included as a new claim by a subsequent amendmentafter the application is filed.

What is claimed is:
 1. A method of performing a network entry procedureby a user equipment (UE) in a wireless communication system configuredfor operations across multiple carriers, the method comprising:receiving, by the UE, multi-carrier configuration information through afirst type carrier configured for the UE, the multi-carrierconfiguration information comprising information related to a pluralityof carriers including the first type carrier and a second type carrierconfigured for the UE, the first type carrier being configured toperform a network entry procedure, the second type carrier beingdifferent from the first type carrier; receiving, by the UE, mobilitycontrol information through the first type carrier, the mobility controlinformation including bandwidth change information and center frequencychange information indicating a change to a bandwidth and a centerfrequency of the first type carrier; performing, by the UE, the networkentry procedure via the changed first type carrier; and receiving asignal through the changed first type carrier by the UE, and wherein thefirst type carrier is changeable only during the network entryprocedure.
 2. The method of claim 1, wherein the network entry procedureis triggered based on a load status.
 3. The method of claim 1, whereinthe network entry procedure is triggered based on a channel condition.4. The method of claim 1, wherein the carrier change information isreceived as a type of a superframe header (SFH).
 5. The method of claim1, wherein the first type carrier corresponds to a primary carrier andthe second type carrier corresponds to a secondary carrier.
 6. A userequipment (UE) configured to perform a network entry procedure in awireless communication system configured for operations across multiplecarriers, the UE comprising: a receiver; and a processor operativelyconnected to the receiver and configured to: receive multi-carrierconfiguration information through a first type carrier configured forthe UE, the multi-carrier configuration information comprisinginformation related to a plurality of carriers including the first typecarrier and a second type carrier configured for the UE, the first typecarrier being configured to perform a network entry procedure, thesecond type carrier being different from the first type carrier; receivemobility control information through the first type carrier, themobility control information including bandwidth change information andcenter frequency change information indicating a change to a bandwidthand a center frequency of the first type carrier; perform the networkentry procedure via the changed first type carrier; and receive a signalthrough the changed first type carrier, and wherein the first typecarrier is changeable only during the network entry procedure.
 7. The UEof claim 6, wherein the network entry procedure is triggered based on aload status.
 8. The UE of claim 6, wherein the network entry procedureis triggered based on a channel condition.
 9. The UE of claim 6, whereinthe carrier change information is received as a type of a superframeheader (SFH).
 10. The UE of claim 6, wherein the first type carriercorresponds to a primary carrier and the second type carrier correspondsto a secondary carrier.